Search results for "PAM"
showing 10 items of 1768 documents
Dopamine D2/3 receptor occupancy by quetiapine in striatal and extrastriatal areas
2010
Quetiapine is next to clozapine an antipsychotic agent that exerts hardly any extrapyramidal side-effects at clinical efficacious doses. Some previous receptor occupancy studies reported preferential extrastriatal D2/3 receptor (D2/3R)-binding properties of second-generation antipsychotics and suggested this as possible reason for improved tolerability. This positron emission tomography (PET) investigation was designed to compare the occupancy of dopamine D2/3Rs by quetiapine in striatal and extrastriatal brain regions. Therefore, a cohort of 16 quetiapine-treated psychotic patients underwent an [18F]fallypride (FP) PET scan. Due to the high affinity of FP and its comparatively long half-li…
Chronic alcohol intake abolishes the relationship between dopamine synthesis capacity and learning signals in ventral striatum
2014
Drugs of abuse elicit dopamine release in the ventral striatum, possibly biasing dopamine-driven reinforcement learning towards drug-related reward at the expense of non-drug-related reward. Indeed, in alcohol-dependent patients, reactivity in dopaminergic target areas is shifted from non-drug-related stimuli towards drug-related stimuli. Such 'hijacked' dopamine signals may impair flexible learning from non-drug-related rewards, and thus promote craving for the drug of abuse. Here, we used functional magnetic resonance imaging to measure ventral striatal activation by reward prediction errors (RPEs) during a probabilistic reversal learning task in recently detoxified alcohol-dependent pati…
Ventral striatal prediction error signaling is associated with dopamine synthesis capacity and fluid intelligence.
2012
Fluid intelligence represents the capacity for flexible problem solving and rapid behavioral adaptation. Rewards drive flexible behavioral adaptation, in part via a teaching signal expressed as reward prediction errors in the ventral striatum, which has been associated with phasic dopamine release in animal studies. We examined a sample of 28 healthy male adults using multimodal imaging and biological parametric mapping with 1) functional magnetic resonance imaging during a reversal learning task and 2) in a subsample of 17 subjects also with positron emission tomography using 6-[18F]fluoro-L-DOPA to assess dopamine synthesis capacity. Fluid intelligence was measured using a battery of nine…
Dopamine-modulated aversive emotion processing fails in alcohol-dependent patients.
2013
Negative mood states after alco- hol detoxifi cation may enhance the relapse risk. As recently shown in healthy volunteers, dopamine storage capacity ( V d ) in the left amy- gdala was positively correlated with functional activation in the left amygdala and anterior cin- gulate cortex (ACC) during an emotional task; high functional connectivity between the amy- gdala and the ACC, a region important for emo- tion regulation, was associated with low trait anxiety. Based on these fi ndings, we now tested whether detoxifi ed alcohol-dependent patients have a disrupted modulation of the anterior cin- gulate cortex activation in response to aversive stimuli by amygdala dopamine. Furthermore, we …
'Prefrontal' cognitive performance of healthy subjects positively correlates with cerebral FDOPA influx: an exploratory [18F]-fluoro-L-DOPA-PET inves…
2006
Dopamine neurotransmission influences those cognitive processes, which are generally regarded as prefrontal cortical functions. In previous positron‐emission‐tomography (PET) studies, net blood‐brain clearance of [(18)F]‐fluoro‐l‐DOPA (FDOPA) correlated with impaired cognitive performance in patients with Parkinson's disease or schizophrenia. We hypothesized that FDOPA influx also correlates with performance of cognitive tasks associated with prefrontal functioning in healthy volunteers. The net blood‐brain clearance of FDOPA (K [Formula: see text]) was mapped in a group of 11 healthy volunteers and calculated in striatal volumes‐of‐interest. The Wisconsin‐Card‐Sorting‐Test (WCST), Stroop‐T…
Dopamine in amygdala gates limbic processing of aversive stimuli in humans
2008
Dopamine is known to contribute to the amygdala-mediated aversive response, where increased dopamine release can augment amygdala function. Combining fMRI and PET imaging techniques, Kienast et al. present findings that suggest a functional link between anxiety temperament, dopamine storage capacity and emotional processing in the amygdala. Dopamine is released under stress and modulates processing of aversive stimuli. We found that dopamine storage capacity in human amygdala, measured with 6-[18F]fluoro-L-DOPA positron emission tomography, was positively correlated with functional magnetic resonance imaging blood oxygen level–dependent signal changes in amygdala and dorsal anterior cingula…
No evidence for attenuated stress-induced extrastriatal dopamine signaling in psychotic disorder
2015
AbstractStress is an important risk factor in the etiology of psychotic disorder. Preclinical work has shown that stress primarily increases dopamine (DA) transmission in the frontal cortex. Given that DA-mediated hypofrontality is hypothesized to be a cardinal feature of psychotic disorder, stress-related extrastriatal DA release may be altered in psychotic disorder. Here we quantified for the first time stress-induced extrastriatal DA release and the spatial extent of extrastriatal DA release in individuals with non-affective psychotic disorder (NAPD). Twelve healthy volunteers (HV) and 12 matched drug-free NAPD patients underwent a single infusion [18F]fallypride positron emission tomogr…
Net influx of plasma 6-[18F]fluoro-L-DOPA (FDOPA) to the ventral striatum correlates with prefrontal processing of affective stimuli.
2006
Dopaminergic neurotransmission in the ventral and dorsal striatum interact with central processing of rewarding and reward-indicating stimuli, and may affect frontocortical-striatal-thalamic circuits regulating goal-directed behaviour. Thirteen healthy male volunteers were investigated with multimodal imaging, using the radioligand 6-[ 18 F]fluoro-L-DOPA (FDOPA) for positron emission tomography (PET) measurements of dopamine synthesis capacity, and also functional magnetic resonance imaging (fMRI) in a cognitive activation paradigm. We calculated the correlation between FDOPA net blood-brain influx (K app in ; ml/g/min) in the ventral and associative dorsal striatum and BOLD signal changes …
Decreased dopamine D2/D3-receptor binding in temporal lobe epilepsy: an [18F]fallypride PET study.
2006
Summary: Purpose: Although animal data are suggestive, evidence for an alteration of the extrastriatal dopaminergic system in human focal epilepsy is missing. Methods: To quantify D2/D3-receptor density, we studied seven patients with temporal lobe epilepsy (TLE) and nine agematched controls with positron emission tomography (PET) by using the high-affinity dopamine D2/D3-receptor ligand [ 18 F]Fallypride ([ 18 F]FP) suitable for imaging extrastriatal binding. TLE was defined by interictal and ictal video-EEG, magnetic resonance imaging (MRI), and [ 18 F]fluorodeoxyglucose ([ 18 F]FDG)-PET and was due to hippocampal sclerosis (HS), based on histology in all patients. Primary analysis was ba…
Reduced Cerebral Fluoro-l-Dopamine Uptake in Adult Patients Suffering from Phenylketonuria
2007
Deficiency of phenylalanine hydroxylase activity in phenylketonuria (PKU) causes an excess of phenylalanine (Phe) throughout the body, predicting impaired synthesis of catecholamines in the brain. To test this hypothesis, we used positron emission tomography (PET) to measure the utilization of 6-[18F]fluoro-l-dopamine (FDOPA) in the brain of adult patients suffering from PKU and in healthy controls. Dynamic 2-h long FDOPA emission recordings were obtained in seven adult PKU patients (five females, two males; age: 21 to 27 years) with elevated serum Phe levels, but lacking neurologic deficits. Seven age-matched, healthy volunteers were imaged under identical conditions. The utilization of F…